Sputtering is a process where a solid target material is bombarded with energetic particles and, as a result, atoms of the target material are ejected from the target. Sputtering is commonly used for thin-film depositions in many high-tech applications. Commonly, an argon plasma is used to sputter material from a target and deposit the material on a substrate.
As sputter technology improves, many industries are moving toward larger area substrates upon which thin film depositions are carried out. For example, in the semiconductor industry, processing larger semiconductor wafer substrates provides higher yield of dies used to make computer chips and related circuitry devices. In another example, thin film coatings are used on large format glass substrates for solar cells and windows having high-tech coatings, such as electrochromic devices made of a stack of deposited materials on a glass or other transparent substrate used to make electrochromic (EC) windows. Many such applications require highly-uniform coatings in order to make solar or electrochromic devices that perform well. As technology advances, such coatings become thinner and thinner and thus uniformity of the layers making up such coatings must be commensurately higher.
Non-uniformity of a sputter deposited layer becomes more of an issue with the use of larger substrates because it is a challenge to coat a large area with a consistently high uniformity. For example, the morphology, coverage and/or thickness of the deposited material may be different in different areas of the substrate. These variations may be due to corresponding variations in plasma density, which in some instances can correlate to non-uniformity in the sputter target and/or the use of sectioned sputter targets.